Pienaar receives the 1995 rugby World Cup from Mandela: 'During those six weeks what happened was incredible.' Photograph: Philip Littleton/AFP/Getty Images

Among certain white communities in apartheid South Africa, it was taken for granted that Nelson Mandela was a terrorist who must remain behind bars. That was drummed into the young François Pienaar, who would one day welcome Mandela to his wedding and name him as godfather to his two sons.

The men came together when Pienaar captained South Africa to victory at the 1995 Rugby World Cup. When the blond Afrikaner shook hands with the black freedom fighter turned president, they instantly forged one of the country's defining images of racial unity.

"François here is the symbol of reconciliation," said Ahmed Kathrada, a fellow prisoner of Mandela on Robben Island, when he shared a platform with Pienaar at the One Young World summit in Johannesburg last October.

In an interview with the Observer, Pienaar recalled the hardline white attitudes that shaped his childhood. "In my little world, I grew up in an Afrikaner community, went to an Afrikaner school, spoke only Afrikaans. Children were seen and not heard and you believed the publicity of the day," he said. "Obviously the press told the stories that the ruling party of the day in particular wanted to be told.

"I remember when I heard Nelson Mandela's name mentioned at barbecues or dinner parties, the words 'terrorist' or 'bad man' was an umbilical cord almost to his name. As a young kid I wish I'd had questions about it, but I never did. I just thought that guy's maybe not a good guy, because sadly we didn't engage with our parents.

"You didn't ask questions like why black kids don't go to school with you, why is it just all white? That's how you grew up, which is very wrong and very sad. I wish I'd had the courage of conviction to ask questions, but I didn't. It's about exposure."

It was only when Pienaar went to university on a sports scholarship that he found himself exposed to different cultures, speaking English and having debates about politics and the country's future. "We'd just gone through 1985, a very dark year in South Africa's history, so it was topical at university. There were talks and rumours about Mr Mandela being released and white South Africans in particular feared the worst.

"Many were very conservative South Africans who were stocking up on food, thinking it's going to be Armageddon, civil warfare. I can understand that, not that I agreed with it. They feared that if this man who had been put in jail for 27 years, and was not handled particularly well as a prisoner, comes out, he's going to be slightly peeved.

"What he says the nation will do. So if Mr Mandela came out of prison and said, 'Listen, this is wrong, we're taking over the country now by force,' it would have been civil warfare. Then he came out and he didn't. The conservative people were, 'We're just waiting for this to happen'. It never happened."

Mandela's release and the fall of apartheid meant an end to international sanctions and sporting boycotts. A year after the first multiracial democratic election in 1994, the country hosted the Rugby World Cup, traditionally an Afrikaner sport that saw black people cheering for the opposition. But Mandela understood the importance of surprise and the grand gesture. He resisted pressure to scrap the springbok, the team's despised emblem, and rallied the nation around the players.

"During those six weeks what happened in this country was incredible," Pienaar said. "I'm still gobsmacked when I think back to the profound change that happened. We started obviously with a great leader with a fantastic vision who realised that sport is important for the Afrikaner white community and to earn their respect and trust.

"But on the other side I have such a respect for what he had to go through in the African National Congress because the springbok was a symbol of apartheid. The majority of South Africans never supported the Springboks, so to ask them to support them for the first time was a massive ask.

"Through the course of those six weeks, because he asked them and we came to the party in terms of playing good rugby and building a nice momentum towards the final, things happened in South Africa that were just magical."

For the final there were 63,000 people in the stadium and 62,000 were white. With a stroke of PR genius, Mandela appeared in the green-and-gold Springbok jersey and cap: "It's well documented that Mr Mandela walked out into Ellis Park in front of a predominantly white crowd, very much an Afrikaner crowd, wearing a springbok on his heart and how they shouted, 'Nelson, Nelson, Nelson!' because what he'd promised he delivered. And when the final whistle blew this country changed for ever. It's incomprehensible."

The events became the subject of a book and film, Invictus, starring Matt Damon and Morgan Freeman and directed by Clint Eastwood. Pienaar and Mandela became close over the years until ill health forced the latter to withdraw from public life. Last week came the sad but inevitable news of his demise.

"It's a time for celebration, celebrating what he did and what he stood for, and also time for reflection and mourning obviously," Pienaar said.

"But hopefully it will be tears of joy that South Africa has been so blessed to have a man who put us on a very important road, and just hope the leaders following him will not only use his name for effect but because they truly believe in what he stood for, and build on that."